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> Reference material for ROW_NUMBER function

# ROW_NUMBER OVER

Returns a unique row number for each row within the requested window.

For more information on usage, please refer to [Window Functions](/reference-sql/functions-reference/window).

## Syntax

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
ROW_NUMBER() OVER ([PARTITION BY <partition_by>] ORDER BY <order_by> [ASC|DESC] )
```

## Parameters

| Parameter        | Description                                                                                                       | Supported input types |
| :--------------- | :---------------------------------------------------------------------------------------------------------------- | :-------------------- |
| `<partition_by>` | The expression used for the `PARTITION BY` clause.                                                                | Any                   |
| `<order_by>`     | The expression used in the `ORDER BY` clause. This parameter determines what value will be used for `ROW_NUMBER`. | Any                   |

## Return Type

`INTEGER`

## Example

In this example below, players in each game level are assigned a player ID.

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT
	nickname,
	level,
	ROW_NUMBER() OVER (PARTITION BY level ORDER BY level ASC ) AS player_id
FROM
	players;
```

**Returns**:

| nickname    | level | player\_id |
| :---------- | :---- | :--------- |
| ymatthews   | 9     | 1          |
| rileyjon    | 12    | 2          |
| sabrina21   | 11    | 3          |
| burchdenise | 10    | 4          |